The present invention relates to the field of acoustic wave devices, and particularly to that of transducers capable of operating at very high frequencies, from a few hundred MHz to several gigahertz.
A number of patent applications are known that describe passive devices for processing RF signals, which comprise comb structures having interdigitated electrodes and apply the mechanism known as “interface waves.” This type of device requires utilization of a polymer film that ensures an elastic connection between the materials; this produces considerable acoustic losses. Although certain configurations allow this type of organic layer to be omitted, they nevertheless require the development of technologies that allow integration with the interface of said interdigitated transducer, which is known to present technological difficulties.
Also known are narrow-gap transducers comprising electrodes of optimized width, in which the distance between electrodes is greatly reduced. In order to operate e.g. at 1.6 GHz, however, the electrodes having a width of 1.5 μm (or λ/2) must be separated by a distance on the order of a few hundredths of angstroms, requiring technology that is tricky to implement.
To eliminate these disadvantages, Patent Application FR 2811828 is known; this describes a surface acoustic wave device comprising a layer of ferroelectric material and a substrate, and characterized in that the layer of ferroelectric material is contained between a first electrode and a second electrode, and that the layer of ferroelectric material has first positive-polarization domains and second negative-polarization domains, the first and second domains being alternated.